[Coco] RS232 Pak needed

[Gene Heskett]

On Friday 20 September 2013 13:35:42 William Astle did opine:

> Mark can probably straighten out any misunderstanding on my part, but as
> I understand it, you can completely ignore the SCS signal and other
> miscellaneous dumbness in the design and just decode the address lines
> directly. I believe asserting SLENB disables the internal address
> decoding stuff in some manner so if you decode the address and determine
> it's yours, you assert SLENB and basically take control. Thus, no need
> to adjust the hardware inside the machine.

This works from the MPI?  Great, in my best Tony the Tiger voice...
> 
> You have to be careful with PIA0, though. You can't re-purpose
> FF1C..FF1F - later versions of the Color Basic ROM actually use that
> ghost address during initialization.

Who at this late date, can we kill for that? OTOH, thats only 1, 4 byte 
wide block.  Still leaves 13 of them that we could have a ball with.
> 
> On 2013-09-20 10:55, Gene Heskett wrote:
> > On Friday 20 September 2013 12:23:54 William Astle did opine:
> >> On 2013-09-20 06:08, Gene Heskett wrote:
> >>> Assuming we do a 2 port version, and we could offer it for $60 by
> >>> the time we get gold flashed boards, find out who made the cases
> >>> Roger used, get some of those & modify that one for a pair of
> >>> db9's, how many of you folks would buy it in the next year?
> >> 
> >> I would certainly consider it as long as shipping outside the United
> >> States is not going to be a problem. I might even consider more than
> >> one if they have a selectable base address. I suspect I would be
> >> using them in systems without a FDC so I could easily put a couple
> >> in the FF4x range.
> > 
> > Base addressing agility is a good point William.  In fact, that might
> > be something we could do preparatory to this.  Unforch I suspect it
> > would require trace cuts to do it on the coco's main board, and
> > pasting the newly derived signals back to where they should go.  We
> > have a lot of users who would not be at all comfortable with that,
> > darnit.
> > 
> >> Even better if they can assert SLENB or whatever that signal is
> >> called to open up the range of base addresses they can use even
> >> further. If I have my facts straight, that might even allow for
> >> putting them in the FF3x range.
> > 
> > There are 7 usable 4 byte wide slots between the 2 PIA's on the main
> > board, and another 7 such slots between the 2nd PIA and the disk
> > controller. I'd like to isolate those 2 PIA's and ship the rest of it
> > out to the MPI, but with the sloppy decoding in existing packs, we
> > would likely break a few of those.  A tiny board, programmable to
> > decode any one or two of those 4 byte wide addresses might be a
> > project to consider though, basically fixing the charley foxtrots Ft
> > Worth gave us.  But this falls backwards too because if we go hanging
> > them here and there willy-nilly, using old ttl logic, we will soon be
> > in need of a 6x09 to address bus buffer, at least on the 6809
> > machines.  For the 63C09's, mine at least, looks to be capable of
> > driving nearly any amount of such loads as it pulls what loads it has
> > to within a very few millivolts of the supply rails, doing it nearly
> > as fast as my dual trace 100mhz scope can display.  In modern 10
> > nanosecond CMOS, that would be a non-problem today.  Let me cogitate
> > on that.  It could be a case of clipping off & removing the existing
> > 76LS138 and using that board pad to insert the newer decoding.  If
> > that kills SLENB, then we might be able to combine the leftovers and
> > make a new SLENB.
> > 
> > What if's, gotta love 'em.
> > 
> >> --
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> >> Coco at maltedmedia.com
> >> http://five.pairlist.net/mailman/listinfo/coco
> > 
> > Cheers, Gene
> 
> --
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> Coco at maltedmedia.com
> http://five.pairlist.net/mailman/listinfo/coco


Cheers, Gene
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